First‐Trimester Nuchal Translucency Screening

Abstract

To the Editor: Chasen and colleagues 1 in their editorial "Prenatal Informed Consent for Sonogram: The Time for First-Trimester Nuchal Translucency Has Come" 1 correctly point out that nuchal translucency (NT) is a useful marker in prenatal screening for Down syndrome and in competent hands could be used for this purpose. The main unresolved issue, however, is how this measurement should be used in screening. Table 1 compares the false-positive rates of different tests, all used to achieve an 85% detection rate. With NT and maternal age, the false-positive rate is 18%, far higher than for other tests in which NT is included: 4.8% for the first-trimester combined test and 0.8% with the first-and second-trimester integrated test.The evidence indicates that NT alone or with maternal age should not be used as a screening test for Down syndrome. As Chasen and colleagues say in their editorial, seeking independent corroboration of the comparative performance of the different markers, alone and in combination with assessment of the implications for screening practice, is a current research issue. These are the main objectives of studies such as the First-and SecondTrimester Evaluation of Risk for Aneuploidy (FASTER) trial in the United States and the Serum, Urine, and Ultrasound Screening Study in Britain.The issue is not whether NT measurement is useful in screening but establishing how it should be used in combination with other screening markers to maximize detection of affected pregnancies and minimize the number of false-positive results in a cost-effective way.